Patient Transport Apparatus With Controlled Auxiliary Wheel Deployment

ABSTRACT

A patient transport apparatus transports a patient over a floor surface. The patient transport apparatus comprises a support structure and support wheels coupled to the support structure. An auxiliary wheel is coupled to the support frame to influence motion of the patient transport apparatus over a floor surface. The auxiliary wheel is movable to a deployed position with the auxiliary wheel engaging the floor surface and a stowed position with the auxiliary wheel spaced a distance from the floor surface. An actuator assembly coupled to the support frame and to the auxiliary wheel. The actuator assembly includes a lift actuator and a spring cartridge assembly. The lift actuator is operable to move the auxiliary wheel to the deployed position and to the stowed position. The spring cartridge assembly is configured to bias the auxiliary wheel towards the deployed position.

CROSS-REFERENCE TO RELATED APPLICATIONS

The subject patent application is a Continuation of U.S. patentapplication Ser. No. 16/690,217, filed on Nov. 21, 2019, which claimspriority to and all the benefits of U.S. Provisional Patent ApplicationNo. 62/770,458, filed on Nov. 21, 2018, the disclosures of each of whichare hereby incorporated by reference in their entirety.

BACKGROUND

Patient transport systems facilitate care of patients in a health caresetting. Patient transport systems comprise patient transportapparatuses such as, for example, hospital beds, stretchers, cots,tables, wheelchairs, and chairs to move patients between locations. Aconventional patient transport apparatus comprises a base, a patientsupport surface, and several support wheels, such as four swivelingcaster wheels. Often, the patient transport apparatus has one or morenon-swiveling auxiliary wheels, in addition to the four caster wheels.The auxiliary wheel, by virtue of its non-swiveling nature, is employedto help control movement of the patient transport apparatus over a floorsurface in certain situations.

When a caregiver wishes to use the auxiliary wheel to help controlmovement of the patient transport apparatus, such as down long hallwaysor around corners, the caregiver selectively moves the auxiliary wheelfrom a stowed position, out of contact with the floor surface, to adeployed position in contact with the floor surface. In many cases,however, as the patient transport apparatus travels over an uneven floorsurface, the auxiliary wheel is unable to make sufficient adjustments inits vertical position to address peaks and valleys in the floor surface.This may result in a loss of traction between the auxiliary wheel andthe floor surface as the patient transport apparatus transitions from aflat surface to a declined surface, or an abrupt transfer of force fromthe auxiliary wheel to the patient transport apparatus as the patienttransport apparatus transitions from a flat surface to an inclinedsurface. Thus, the caregiver must remember to adjust the speed of travelof the patient transport apparatus when traveling over uneven floorsurfaces.

A patient transport apparatus designed to overcome one or more of theaforementioned challenges is desired.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a patient transport apparatus.

FIG. 2 is a perspective view of an auxiliary wheel assembly of thepatient transport apparatus coupled to a base of the patient transportapparatus.

FIG. 3 is a perspective view of the auxiliary wheel assembly comprisingan auxiliary wheel, a lift actuator, and a spring cartridge assembly.

FIG. 4 is an elevation view of the auxiliary wheel assembly shown inFIG. 3 .

FIG. 5 is a perspective view of a portion of the auxiliary wheelassembly shown in FIG. 3 .

FIG. 6 is another perspective view of a portion the auxiliary wheelassembly shown in FIG. 3 .

FIG. 7 is a perspective view of the lift actuator assembly that may beused with the auxiliary wheel assembly shown in FIG. 3 .

FIGS. 8A and 8B are elevation views of the spring cartridge assembly.

FIG. 9A is an elevation view of the auxiliary wheel assembly in adeployed position.

FIG. 9B is an elevation view of the auxiliary wheel assembly in a stowedposition.

FIGS. 10A-10C are elevation views illustrating a movement of theauxiliary wheel with the auxiliary wheel assembly in the deployedposition.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to FIG. 1 , a patient transport system comprising a patienttransport apparatus 20 is shown for supporting a patient in a healthcare setting. The patient transport apparatus 20 illustrated in FIG. 1comprises a hospital bed. In other embodiments, however, the patienttransport apparatus 20 may comprise a cot, table, wheelchair, chair, orsimilar apparatus, utilized in the care of a patient to transport thepatient between locations.

A support structure 22 provides support for the patient. The supportstructure 22 illustrated in FIG. 1 comprises a base 24 and anintermediate frame 26. The base 24 defines a longitudinal axis 28 from ahead end to a foot end. The intermediate frame 26 is spaced above thebase 24. The support structure 22 also comprises a patient support deck30 disposed on the intermediate frame 26. The patient support deck 30comprises several sections, some of which articulate (e.g., pivot)relative to the intermediate frame 26, such as a fowler section, a seatsection, a thigh section, and a foot section. The patient support deck30 provides a patient support surface 32 upon which the patient issupported.

A mattress, although not shown, may be disposed on the patient supportdeck 30. The mattress comprises a secondary patient support surface uponwhich the patient is supported. The base 24, intermediate frame 26,patient support deck 30, and patient support surface 32 each have a headend and a foot end corresponding to designated placement of thepatient's head and feet on the patient transport apparatus 20. Theconstruction of the support structure 22 may take on any known orconventional design, and is not limited to that specifically set forthabove. In addition, the mattress may be omitted in certain embodiments,such that the patient rests directly on the patient support surface 32.

Side rails 38, 40, 42, 44 are supported by the base 24. A first siderail 38 is positioned at a right head end of the intermediate frame 26.A second side rail 40 is positioned at a right foot end of theintermediate frame 26. A third side rail 42 is positioned at a left headend of the intermediate frame 26. A fourth side rail 44 is positioned ata left foot end of the intermediate frame 26. If the patient transportapparatus 20 is a stretcher, there may be fewer side rails. The siderails 38, 40, 42, 44 are movable between a raised position in which theyblock ingress and egress into and out of the patient transport apparatus20 and a lowered position in which they are not an obstacle to suchingress and egress. The side rails 38, 40, 42, 44 may also be movable toone or more intermediate positions between the raised position and thelowered position. In still other configurations, the patient transportapparatus 20 may not comprise any side rails.

A headboard 46 and a footboard 48 are coupled to the intermediate frame26. In other embodiments, when the headboard 46 and footboard 48 areprovided, the headboard 46 and footboard 48 may be coupled to otherlocations on the patient transport apparatus 20, such as the base 24. Instill other embodiments, the patient transport apparatus 20 does notcomprise the headboard 46 and/or the footboard 48.

User interfaces 50, such as handles, are shown integrated into thefootboard 48 and side rails 38, 40, 42, 44 to facilitate movement of thepatient transport apparatus 20 over floor surfaces. Additional userinterfaces 50 may be integrated into the headboard 46 and/or othercomponents of the patient transport apparatus 20. The user interfaces 50are graspable by the user to manipulate the patient transport apparatus20 for movement.

Other forms of the user interface 50 are also contemplated. The userinterface 50 may simply be a surface on the patient transport apparatus20 upon which the user logically applies force to cause movement of thepatient transport apparatus 20 in one or more directions, also referredto as a push location. This may comprise one or more surfaces on theintermediate frame 26 or base 24. This could also comprise one or moresurfaces on or adjacent to the headboard 46, footboard 48, and/or siderails 38, 40, 42, 44.

In the embodiments shown, one set of user interfaces 50 comprises afirst handle 52 and a second handle 54. The first and second handles 52,54 are coupled to the intermediate frame 26 proximal to the head end ofthe intermediate frame 26 and on opposite sides of the intermediateframe 26 so that the user may grasp the first handle 52 with one handand the second handle 54 with the other. In other embodiments, the userinterfaces 50 comprise one or more of a joystick, dial, or knob in placeof the first and second handles 52, 54.

Support wheels 56 are coupled to the base 24 to support the base 24 on afloor surface such as a hospital floor. The support wheels 56 allow thepatient transport apparatus 20 to move in any direction along the floorsurface by swiveling to assume a trailing orientation relative to adesired direction of movement. In the embodiments shown, the supportwheels 56 comprise four support wheels each arranged in corners of thebase 24. The support wheels 56 shown are caster wheels able to rotateand swivel about swivel axes 58 during transport. Each of the supportwheels 56 forms part of a caster assembly 60. Each caster assembly 60 ismounted to the base 24. It should be understood that variousconfigurations of the caster assemblies 60 are contemplated. Inaddition, in some embodiments, the support wheels 56 are not casterwheels and may be non-steerable, steerable, non-powered, powered, orcombinations thereof. Additional support wheels 56 are alsocontemplated. Referring to FIG. 2 , in the embodiments shown, the base24 includes a support assembly 200 that includes a forward supportmember 202, a rear support member 204, and a pair of opposing sidesupport members 206, 208. The side support members 206, 208 extendbetween the forward support member 202 and the rear support member 204and are orientated parallel to the longitudinal axis 28.

Referring to FIGS. 2-10C, an auxiliary wheel system 210 is coupled tothe base 24. The auxiliary wheel system 210 influences motion of thepatient transport apparatus 20 during transportation over the floorsurface.

Referring to FIGS. 2 and 3 , the auxiliary wheel system 210 includes asupport frame 212 that is coupled to the base 24, an auxiliary wheelassembly 214 that is coupled to the support frame 212 and arranged toarticulate (e.g. pivot) with respect to the support frame 212, and anactuator assembly 216 that is coupled the support frame 212 and theauxiliary wheel assembly 214. The auxiliary wheel assembly 214 includesan auxiliary wheel 218 that is configured to influence motion of thepatient transport apparatus 20 over a floor surface 220. The auxiliarywheel assembly 214 is positionable to a deployed position 222 (shown inFIG. 9A) with the auxiliary wheel 218 engaging the floor surface 220,and a stowed position 224 (shown in FIG. 9B) with the auxiliary wheel218 spaced a vertical distance 226 from the floor surface 220. Theactuator assembly 216 is coupled to the support frame 212 and to theauxiliary wheel assembly 214.

Referring to FIGS. 4, 5, 6, and 7 , the actuator assembly 216 includes alift actuator 228 and a spring cartridge assembly 230. The lift actuator228 is operable to move the auxiliary wheel 218 to the deployed position222 engaging the floor surface and to the stowed position 224 spacedaway from and out of contact with the floor surface. The springcartridge assembly 230 is coupled between the lift actuator 228 and theauxiliary wheel 218, and is configured to transfer a force from the liftactuator 228 to the auxiliary wheel 218 to facilitate moving theauxiliary wheel 218 to the deployed position 222 and to the stowedposition 224. In addition, the spring cartridge assembly 230 isconfigured to bias the auxiliary wheel 218 outwardly from the supportframe 212 and towards the deployed position 222, and to allow a verticalmovement of auxiliary wheel 218 with respect to the support frame 212with the auxiliary wheel assembly 214 in the deployed position 222.

In the embodiments shown, the lift actuator 228 is positionable betweenan extended position 232 (shown in FIG. 9A) and a retracted position 234(shown in FIG. 9B). For example, a movement of the lift actuator 228towards the extended position 232 causes the spring cartridge assembly230 to move the auxiliary wheel 218 towards the deployed position 222. Amovement of the lift actuator 228 towards the retracted position 234causes the spring cartridge assembly 230 to move the auxiliary wheel 218towards the stowed position 224. In addition, the spring cartridgeassembly 230 is configured to allow vertical movement of the auxiliarywheel 218 with the lift actuator 228 in the extended position 232.

The auxiliary wheel 218 influences motion of the patient transportapparatus 20 during transportation over the floor surface when theauxiliary wheel 218 is in the deployed position 222. In someembodiments, the auxiliary wheel assembly 214 comprises an additionalauxiliary wheel movable with the auxiliary wheel 218 between thedeployed position 222 and stowed position 224 via the actuator assembly216.

By deploying the auxiliary wheel 218 on the floor surface, the patienttransport apparatus 20 can be easily moved down long, straight hallwaysor around corners, owing to a non-swiveling nature of the auxiliarywheel 218. When the auxiliary wheel 218 is stowed (see FIG. 9B), thepatient transport apparatus 20 is subject to moving in an undesireddirection due to uncontrollable swiveling of the support wheels 56. Forinstance, during movement down long, straight hallways, the patienttransport apparatus 20 may be susceptible to “dog tracking,” whichrefers to undesirable sideways movement of the patient transportapparatus 20. Additionally, when cornering, without the auxiliary wheel218 deployed, and with all of the support wheels 56 able to swivel,there is no wheel assisting with steering through the corner, unless oneor more of the support wheels 56 are provided with steer lock capabilityand the steer lock is activated.

The auxiliary wheel 218 may be arranged parallel to the longitudinalaxis 28 of the base 24. Said differently, the auxiliary wheel 218rotates about a rotational axis R (see FIG. 2 ) oriented perpendicularlyto the longitudinal axis 28 of the base 24 (albeit offset in some casesfrom the longitudinal axis 28). In the embodiments shown, the auxiliarywheel 218 is incapable of swiveling about a swivel axis. In otherembodiments, the auxiliary wheel 218 may be capable of swiveling, butcan be locked in a steer lock position in which the auxiliary wheel 218is locked to solely rotate about the rotational axis R orientedperpendicularly to the longitudinal axis 28. In still other embodiments,the auxiliary wheel 218 may be able to freely swivel without any steerlock functionality.

The auxiliary wheel 218 may be located to be deployed inside a perimeterof the base 24 and/or within a support wheel perimeter defined by theswivel axes 58 of the support wheels 56. In some embodiments, such asthose employing a single auxiliary wheel 218, the auxiliary wheel 218may be located near a center of the support wheel perimeter, or offsetfrom the center. In this case, the auxiliary wheel 218 may also bereferred to as a fifth wheel. In other embodiments, the auxiliary wheel218 may be disposed along the support wheel perimeter or outside of thesupport wheel perimeter. In the embodiments shown, the auxiliary wheel218 has a diameter larger than a diameter of the support wheels 56. Inother embodiments, the auxiliary wheel 218 may have the same or asmaller diameter than the support wheels 56.

As the patient transport apparatus 20 travels over an uneven floorsurface, the spring cartridge assembly 230 allows the auxiliary wheel218 to move vertically with respect to base 24, and biases the auxiliarywheel 218 towards the floor surface with sufficient force to maintaintraction between the floor surface and the auxiliary wheel 218. Inaddition, the spring cartridge assembly 230 permits the auxiliary wheel218 to move upward when encountering a high spot in the floor surfaceand to dip lower when encountering a low spot in the floor surface.

For example, FIGS. 10A-10C illustrate a vertical movement of theauxiliary wheel 218 with the auxiliary wheel assembly 214 in thedeployed position 222. With the auxiliary wheel assembly 214 in thedeployed position 222, the spring cartridge assembly 230 biases theauxiliary wheel 218 towards the floor surface 220 such that theauxiliary wheel 218 is spaced a first vertical distance, V1, from thesupport frame 212. In addition, the spring cartridge assembly 230imparts sufficient downward force to the auxiliary wheel 218 to maintainsufficient traction between the auxiliary wheel 218 and the floorsurface 220. During operation, as the patient transport apparatus 20travels over an inclined floor surface 220 such as, for example, aninclined ramp, the spring cartridge assembly 230 allows the auxiliarywheel 218 to move towards the support frame 212 and to a second verticaldistance, V2, from the support frame 212 that is less than the firstvertical distance, V1. In addition, as the patient transport apparatus20 travels over an declining floor surface 220 such as, for example, atrough, the spring cartridge assembly 230 biases the auxiliary wheel 218away from the support frame 212 and towards a third vertical distance,V3, from the support frame 212 that is greater than the first verticaldistance, V1. By enabling the auxiliary wheel 218 to travel verticallywith respect to the support frame 212 with the auxiliary wheel assembly214 in the deployed position 222, the spring cartridge assembly 230facilitates maintaining sufficient traction between an uneven floorsurface 220 and the auxiliary wheel 218 to enable the auxiliary wheel218 to influence motion of the patient transport apparatus 20 duringoperation.

Referring to FIGS. 5, 6, and 7 , in the embodiments shown, the supportframe 212 includes a first cross-member 236 and a second cross-member238. The second cross-member 238 is spaced a distance from the firstcross-member 236 along the longitudinal axis 28. The first cross-member236 and the second cross-member 238 are each coupled between the pair ofopposing side support members 206, 208.

In the embodiments shown, the auxiliary wheel assembly 214 also includesa crank shaft 240 and a wheel support frame 242. The crank shaft 240 iscoupled to the first cross-member 236 with a crank shaft bracket 246that extends outwardly from an outer surface of the first cross-member236. The crank shaft 240 extends along a centerline axis 248 and isrotatably coupled to the first cross-member 236 such that the crankshaft 240 is rotatable about the centerline axis 248. The wheel supportframe 242 extends radially outwardly from the crank shaft 240 such thata rotation of the crank shaft 240 cause a rotation of the wheel supportframe 242 about the centerline axis 248 of the crank shaft 240. Thewheel support frame 242 is coupled to the auxiliary wheel 218 such thata rotation of the crank shaft 240 causes a vertical movement of theauxiliary wheel 218. The auxiliary wheel assembly 214 also includes acrank 250 that extends radially outwardly from the crank shaft 240 suchthat a rotation of the crank 250 causes a rotation of the crank shaft240 about the centerline axis 248 of the crank shaft 240. The crank 250is coupled to the spring cartridge assembly 230 such that a movement ofspring cartridge assembly 230 via the lift actuator 228 causes arotation of the crank shaft 240.

The spring cartridge assembly 230 includes a piston rod 252, a cartridgehousing 254, and a compression spring 256. The piston rod 252 ispivotably coupled to the crank 250 and the cartridge housing 254 iscoupled to the lift actuator 228. The cartridge housing 254 is movablewith respect to the piston rod 252. The compression spring 256 actsbetween the cartridge housing 254 and to the piston rod 252 such that amovement of the cartridge housing 254 causes a movement of the pistonrod 252. In addition, a movement of the piston rod 252 causes a movementof the crank 250 which in turn causing a rotation of the crank shaft 240and wheel support frame 242.

The piston rod 252 extends between a first rod end 258 and a second rodend 260, and is at least partially positioned within the cartridgehousing 254. The cartridge housing 254 includes a plurality of sidewalls262 extending between a first end 264 and a second end 266. A guideplate 268 is coupled to the plurality of sidewalls 262 and is positionedat the first end 264 of the cartridge housing 254. The guide plate 268includes a rod opening 270 that is defined through the guide plate 268.The rod opening 270 is sized and shaped to receive the piston rod 252therethrough. The second rod end 260 extends through the rod opening270. The first rod end 258 is located at an enlarged head of the pistonrod 252 that is sized larger than the rod opening 270 so that the guideplate 268 is able to abut the enlarged head when stowing the auxiliarywheel 218. The enlarged head is pivotably coupled to the crank 250 via afastening pin extending through the enlarged head and the crank 250. Thesecond rod end 260 is positioned with the cartridge housing 254 andextends toward the second end 266 of the cartridge housing 254. Thesecond rod end 260 is considered a free end, unconnected to any otherstructure.

The compression spring 256 extends between a first end 272 and a secondend 274 and is positioned with the cartridge housing 254 such that thecompression spring 256 surrounds a portion of the piston rod 252. Thecompression spring 256 is configured to bias the cartridge housing 254towards the first rod end 258. The first end 272 of the compressionspring 256 engages the guide plate 268 of the cartridge housing 254 andthe second end 274 of the compression spring 256 acts against the pistonrod 252 via a guide assembly 276 described below.

In the embodiments shown, the spring cartridge assembly 230 includes theguide assembly 276 that is coupled to the piston rod 252 and engages thecompression spring 256. The guide assembly 276 includes a guide ring 278that is coupled to the piston rod 252 and engages the compression spring256. The guide ring 278 includes a pair of opposing positioning flanges280 that extend outwardly from an outer surface of the guide ring 278.Each sidewall 262 of the cartridge housing 254 includes a guide slot 282that extends through the sidewall 262. Each positioning flange 280 isinserted through a corresponding guide slot 282 to support the pistonrod 252 from the cartridge housing 254. Each positioning flange 280 isslideably engaged within the guide slot 282 to enable the cartridgehousing 254 to move with respect to the piston rod 252. In addition, theguide slots 282 are sized and shaped to allow a movement of the pistonrod 252 with respect to the cartridge housing 254 with the lift actuator228 in the extended position 232. For example, the guide slot 282includes a length that enables the guide ring 278 to slide along alength of the guide slot 282 to enable the piston rod 252 to translaterelative to the cartridge housing 254.

In some embodiments, the guide assembly 276 includes a biasing loadadjustment assembly 284 for adjusting a load imparted by the compressionspring 256. In the illustrated embodiment, the biasing load adjustmentassembly 284 includes an adjustment member 285 (see FIGS. 8A and 8B)that is coupled to the piston rod 252 and engages the guide ring 278 foradjusting an operating length of the compression spring 256 to adjust aload imparted by the compression spring 256 onto the piston rod 252 andcartridge housing 254. In addition, the biasing load adjustment assembly284 enables a service technician to release the tension of thecompression spring 256 thereby removing the biasing force on theauxiliary wheel 218 to enable the service technician to safely servicethe actuator assembly 216.

For example, the piston rod 252 may include an outer surface having athreaded portion 283. The adjustment member 285 may comprise atensioning nut, threadably coupled to piston rod 252 along the threadedportion 283 such that a rotation of the tensioning nut with respect tothe piston rod 252 adjusts the length of the compression spring 256. Forexample, a rotation of the tensioning nut in a first rotationaldirection 287 moves the tensioning nut 285 and the guide ring 278 alongthe piston rod 252 in a first linear direction 289 that decreases thelength of the compression spring 256 to preload a compressive force ontothe compression spring 256. A rotation of the tensioning nut 285 in asecond opposite rotational direction 291 moves the tensioning nut 285and the guide ring 278 along the piston rod 252 in a second lineardirection 293 that increases the length of the compression spring 256 toreduce the compressive force of the compression spring 256. In addition,during normal operation, the compression spring 256 is in compression inall positions. In order to service the actuator assembly 216, theservice technician may remove the compression on the compression spring256 by loosening the tensioning nut 285, thereby allowing the servicetechnician to safely remove the crank 240 pin and service the actuatorassembly 216.

Referring to FIGS. 9A and 9B, the actuator assembly 216 includes anactuator support bracket 286 that is hingedly coupled to the secondcross-member 238. The cartridge housing 254 is pivotably coupled to theactuator support bracket 286 via a fastening pin 288 inserted throughthe second end 266 of the cartridge housing 254 and the actuator supportbracket 286. The lift actuator 228 is coupled to the actuator supportbracket 286 such that a movement of the lift actuator 228 causes amovement of the actuator support bracket 286 and the cartridge housing254.

In the embodiments shown, the lift actuator 228 is a linear actuatorthat includes an actuator housing 290 and an actuator rod 292. Theactuator rod 292 has a proximal end received in the actuator housing 290and a distal end spaced from the actuator housing 290. The distal end ofthe actuator rod 292 is configured to be movable relative to theactuator housing 290 to extend and retract an overall length of the liftactuator 228. The actuator rod 292 is movable between the extendedposition 232 (shown in FIG. 9A) with the actuator rod 292 extendingoutwardly from the actuator housing a first distance, and the retractedposition 234 (shown in FIG. 9B) with the actuator rod 292 extendingoutwardly from the actuator housing a second distance that is longerthan the first distance. The actuator housing 290 is coupled to thefirst cross-member 236. The actuator rod 292 is pivotably coupled to theactuator support bracket 286 with a fastening pin 294. The support frame212 includes an actuator support arm 296 that extends outwardly from thefirst cross-member 236. The actuator support arm 296 is coupled to theactuator housing 290 to support the actuator housing 290 from the firstcross-member 236.

In the embodiments shown, the auxiliary wheel assembly 214 also includesan auxiliary wheel drive system 298 (see FIG. 5 ) operatively coupled tothe auxiliary wheel 218. The auxiliary wheel drive system 298 isconfigured to drive (e.g. rotate) the auxiliary wheel 218. In theembodiment shown, the auxiliary wheel drive system 298 includes a motorassembly 300 coupled to a power source 302 such as, for example, abattery for providing electrical power to energize the motor assembly300. The motor assembly 300 that is coupled to the auxiliary wheel 218for rotating the auxiliary wheel 218 about the rotational axis R. Themotor assembly 300 includes a motor assembly housing 304 and a motor 306positioned within the motor assembly housing 304. The motor 306 iscoupled to the auxiliary wheel 218 for providing motive power to theauxiliary wheel 218. The motor assembly housing 304 includes a body(also referred to as a link) that extends between a first housing end308 and a second housing end 310 (see FIG. 6 ). The first housing end308 is pivotably coupled to the wheel support frame 242 via a fastenersuch that a rotation of the crank shaft 240 causes a vertical movementof the motor assembly housing 304 and the auxiliary wheel 218. Thesecond housing end 310 is pivotably coupled to the second cross-member238.

Referring to FIG. 6 , the support frame 212 includes a motor assemblysupport bracket 312 that extends outwardly from the second cross-member238. The motor assembly support bracket 312 is coupled to the motorassembly housing 304 to support the motor assembly housing 304 from thesecond cross-member 238. The motor assembly support bracket 312 includesa translation slot 314 that extends through an outer surface of themotor assembly support bracket 312. The motor assembly housing 304 ispivotably and moveably coupled to the motor assembly support bracket 312with a fastening pin 316 that extends outwardly from the motor assemblyhousing 304 and through the translation slot 314. The motor assemblyhousing 304 is configured to articulate and translate relative to thesecond cross-member 238. The translation slot 314 is sized and shaped toenable the fastening pin 316 to slide along a length of the translationslot 314 to enable the motor assembly housing 304 to translate relativeto the motor assembly support bracket 312.

In some embodiments, the motor assembly 300 includes a gear trainassembly 318 that is coupled to the motor 306 and the auxiliary wheel218 for transferring torque from the motor 306 to the auxiliary wheel218. The gear train assembly 318 may also be positioned within motorassembly housing 304.

In the embodiments shown, referring back to FIG. 9A, during operation,as the lift actuator 228 moves to the extended position, the actuatorrod 292 causes the actuator support bracket 286 to pivot toward thesecond cross-member 238 which causes the cartridge housing 254 to movetowards the second cross-member 238 and away from the crank shaft 240.As the cartridge housing 254 moves toward the second cross-member 238,the guide plate 268 engages and compresses the compression spring 256which, in turn, pushes the piston rod 252 toward the second cross-member238. As the piston rod 252 moves toward the second cross-member 238, thepiston rod 252 causes the crank 250 to rotate the crank shaft 240 andthe wheel support frame 242 in a first rotational direction. Therotation of the wheel support frame 242 causes the motor assemblyhousing 304 and the auxiliary wheel 218 to move away from the supportframe 212 to the deployed position 222. In the deployed position 222,the lift actuator 228 is in the extended position 232 and an outersurface of the actuator support bracket 286 contacts the secondcross-member 238 to prevent further extension of the actuator rod 292.In addition, referring back to FIG. 6 , as the motor assembly housing304 moves away from the support frame 212, the fastening pin 316 slidesalong the translation slot 314 to enable the motor assembly housing 304to pivot and translate relative to the motor assembly support bracket312.

As the lift actuator 228 moves to the retracted position 234, as shownin FIG. 9B, the actuator rod 292 causes the actuator support bracket 286to pivot away from the second cross-member 238 which causes thecartridge housing 254 to move towards the first cross-member 236 andtowards the crank shaft 240. As the cartridge housing 254 moves towardthe crank shaft 240, the guide plate 268 engages the enlarged head ofthe piston rod 252 pivotally connected to the crank 250 which, in turn,causes the crank 250 to rotate the crank shaft 240 and the wheel supportframe 242 in a second opposite rotational direction, which causes themotor assembly housing 304 and the auxiliary wheel 218 to move to thestowed position 224.

Referring to FIGS. 10A-10C, with the with the auxiliary wheel assembly214 in the deployed position 222, as the patient transport apparatus 20travels over uneven floor surfaces, the compression spring 256 providessuspension functions for the auxiliary wheel assembly 214 by actingbetween the cartridge housing 254 and the piston rod 252.

The guide ring 278 moves within the guide slot 282 to enable the pistonrod 252 and compression spring 256 to move with respect to the cartridgehousing 254 which, in turn, allows for a rotation of the crank shaft 240to enable movement of the auxiliary wheel 218 in the vertical direction.By enabling the auxiliary wheel 218 to travel vertically with respect tothe support frame 212 with the auxiliary wheel assembly 214 in thedeployed position 222, the spring cartridge assembly 230 facilitatesmaintaining sufficient traction between an uneven floor surface 220 andthe auxiliary wheel 218 to enable the auxiliary wheel 218 to influencemotion of the patient transport apparatus 20 during operation.

For example, as shown in FIGS. 10A and 10B, as the patient transportapparatus 20 transitions from a flat surface to an inclined floorsurface, the spring cartridge assembly 230 allows the auxiliary wheel218 to move towards the support frame 212. As the downward forceimparted on the auxiliary wheel 218 by the patient transport apparatus20 increases, the crank shaft 240 rotates to move the enlarged head ofthe piston rod 252 away from the cartridge housing 254. The guide ring278 then moves towards the guide plate 268 compressing the compressionspring 256 against the guide plate 268, allowing the compression spring256 to absorb the downward force of the weight of the patient transportapparatus 20.

Referring to FIGS. 10A and 10C, as the patient transport apparatus 20transitions from a flat surface to a declined floor surface, the springcartridge assembly 230 biases the auxiliary wheel 218 away from thesupport frame 212. As the downward force of the patient transportapparatus 20 decreases, the compression spring 256 expands to move theguide ring 278 away from the guide plate 268 which causes the crankshaft 240 to rotate in the opposite direction to move the auxiliarywheel 218 away from the support frame 212 to remain in contact with thedeclining floor surface.

Although an exemplary embodiment of an auxiliary wheel assembly 214 isdescribed above and shown in the figures, it should be appreciated thatother configurations employing a lift actuator 228 to move the auxiliarywheel 218 between the retracted position 234 and deployed position 222are contemplated. A control system and associated controller, one ormore user input devices, and one or more sensors, may be employed tocontrol operation of the lift actuator 228 and the auxiliary wheel drivesystem 298, in the manner described in U.S. patent application Ser. No.16/222,506, hereby incorporated herein by reference.

Several embodiments have been discussed in the foregoing description.However, the embodiments discussed herein are not intended to beexhaustive or limit the invention to any particular form. Theterminology which has been used is intended to be in the nature of wordsof description rather than of limitation. Many modifications andvariations are possible in light of the above teachings and theinvention may be practiced otherwise than as specifically described.

What is claimed is:
 1. A patient transport apparatus comprising: asupport structure arranged for movement along a floor surface; a supportwheel coupled to the support structure, with the support wheel beingswivelable about a swivel axis; and an auxiliary wheel system including:a support frame coupled to the support structure; an auxiliary wheelassembly coupled to the support frame and positionable between adeployed position engaging the floor surface and a stowed positionspaced a from the floor surface, the auxiliary wheel assembly including:an auxiliary wheel configured to influence motion of the patienttransport apparatus over a floor surface, a motor assembly coupled tothe auxiliary wheel and having a motor assembly housing and a motorpositioned within the motor assembly housing and coupled to theauxiliary wheel for providing motive power to the auxiliary wheel, acrank shaft rotatably coupled to the support frame, and a wheel supportframe extending from the crank shaft and coupled to the auxiliary wheelsuch that a rotation of the crank shaft causes a vertical movement ofthe auxiliary wheel; and an actuator assembly coupled to the supportframe and to the auxiliary wheel, the actuator assembly including: alift actuator operable to move the auxiliary wheel to the deployedposition and to the stowed position; and a spring cartridge assemblyconfigured to bias the auxiliary wheel towards the deployed position. 2.The patient transport apparatus of claim 1, wherein the spring cartridgeassembly is configured to allow vertical movement of auxiliary wheelwith respect to the support frame with the auxiliary wheel assembly inthe deployed position.
 3. The patient transport apparatus of claim 1,wherein the spring cartridge assembly is coupled between the liftactuator and the auxiliary wheel for transferring a force from the liftactuator to the auxiliary wheel to facilitate moving the auxiliary wheelto the deployed position and to the stowed position.
 4. The patienttransport apparatus of claim 3, wherein the lift actuator ispositionable between an extended position and a retracted position. 5.The patient transport apparatus of claim 4, wherein the lift actuator ismovable towards the extended position to cause the spring cartridgeassembly to move the auxiliary wheel towards the deployed position, andwherein the lift actuator is movable towards the retracted position tocause the spring cartridge assembly to move the auxiliary wheel towardsthe stowed position.
 6. The patient transport apparatus of claim 5,wherein the spring cartridge assembly is configured to allow verticalmovement of the auxiliary wheel with the lift actuator in the extendedposition.
 7. The patient transport apparatus of claim 1, wherein thesupport frame includes a first cross-member and a second cross-memberspaced a distance from the first cross-member along a longitudinal axis.8. The patient transport apparatus of claim 7, wherein the supportstructure includes a forward support member, a rear support member, apair of opposing side support members extending between the forwardsupport member and the rear support member and orientated along thelongitudinal axis; and wherein each of the first and secondcross-members is coupled between the pair of opposing side supportmembers.
 9. The patient transport apparatus of claim 7, wherein thecrank shaft is rotatably coupled to the first cross-member; and whereinthe wheel support frame extends radially outwardly from the crank shaft.10. The patient transport apparatus of claim 9, wherein the auxiliarywheel assembly includes a crank extending radially outwardly from thecrank shaft and coupled to the spring cartridge assembly such that amovement of spring cartridge assembly causes a rotation of the crankshaft.
 11. The patient transport apparatus of claim 10, wherein thespring cartridge assembly includes: a cartridge housing including aguide plate, the guide plate including a rod opening definedtherethrough; a piston rod at least partially positioned within thecartridge housing, the piston rod extending between a first rod end anda second rod end, the second rod end extending through the rod opening;and a compression spring acting between the piston rod and the cartridgehousing for biasing the cartridge housing towards the first rod end. 12.The patient transport apparatus of claim 11, wherein the springcartridge assembly includes a guide assembly coupled to the piston rodand engaging the compression spring.
 13. The patient transport apparatusof claim 12, wherein the cartridge housing includes a sidewall and aguide slot extending through the sidewall; and wherein the guideassembly includes a guide ring that includes a positioning flangeinserted through the guide slot to support the piston rod from thecartridge housing.
 14. The patient transport apparatus of claim 13,wherein the guide slot is configured to allow a movement of the pistonrod with respect to the cartridge housing with the lift actuator in anextended position.
 15. The patient transport apparatus of claim 13,wherein the guide assembly includes an adjustment member that is coupledto the piston rod for adjusting an operating length of the compressionspring to adjust a load imparted by the compression spring; wherein thepiston rod includes an outer surface having a threaded portion, theadjustment member including a tensioning nut threadably coupled topiston rod, wherein a rotation of the tensioning nut with respect to thepiston rod adjusts the operating length of the compression spring; andwherein a rotation of the tensioning nut in a first rotational directionmoves the tensioning nut along the piston rod in a first lineardirection to decrease the operating length of the compression spring toincrease biasing force of the compression spring, and wherein a rotationof the tensioning nut in a second opposite rotational direction movesthe tensioning nut along the piston rod in a second opposite lineardirection to increase the operating length of the compression spring toreduce biasing force of the compression spring.
 16. The patienttransport apparatus of claim 11, wherein the piston rod is pivotablycoupled to the crank and the cartridge housing is coupled to the liftactuator; and wherein the actuator assembly includes an actuator supportbracket pivotably coupled to the second cross-member, the cartridgehousing being pivotably coupled to the actuator support bracket.
 17. Thepatient transport apparatus of claim 16, wherein the lift actuator iscoupled to the actuator support bracket such that a movement of the liftactuator causes a movement of the actuator support bracket and thecartridge housing; and wherein the lift actuator includes an actuatorhousing and an actuator rod, the actuator rod being movable between anextended position and a retracted position.
 18. The patient transportapparatus of claim 17, wherein the actuator housing is coupled to thefirst cross-member and the actuator rod is pivotably coupled to theactuator support bracket; and wherein the support frame includes anactuator support arm extending outwardly from the first cross-member,the actuator support arm coupled to the actuator housing to support theactuator housing from the first cross-member.
 19. The patient transportapparatus of claim 11, wherein the motor assembly housing includes abody extending between a first housing end and a second housing end, thefirst housing end pivotably coupled to the wheel support frame, thesecond housing end being pivotably coupled to the second cross-member;wherein the support frame includes a motor assembly support bracketextending outwardly from the second cross-member, the motor assemblysupport bracket coupled to the motor assembly housing to support themotor assembly housing from the second cross-member; and wherein themotor assembly support bracket includes a translation slot extendingtherethrough, the motor assembly housing being pivotably and moveablycoupled to the motor assembly support bracket with a pin extendingoutwardly from the motor assembly housing and through the translationslot.
 20. The patient transport apparatus of claim 1, wherein the motorassembly includes a gear train assembly coupled to the motor and theauxiliary wheel for transferring torque from the motor to the auxiliarywheel.